A domain name which specifies the mailbox for the person responsible for this domain. Its format in master files uses the DNS convention for mailbox encoding, identical to that used for the RNAME mailbox field in the SOA RR. The root domain name (just ".") may be specified to indicate that no mailbox is available.

A domain name identifying TXT RRs. A subsequent query can be performed to retrieve the associated TXT records. This provides a level of indirection so that the entity can be referred to from multiple places in the DNS. The root domain name (just ".") may be specified to indicate that no associated TXT RR exists.